The present invention relates generally to magnetic disk devices, and more particularly, to a magnetic disk device suitable for preventing trouble from arising from use of a lubricant when flying height of a magnetic head is reduced for enhanced recording density.
In magnetic disk devices each including magnetic head sliders, density at which information can be recorded on a magnetic disk will increase as the clearance between the spinning magnetic disk and a magnetic head for recording/reading information on/from the magnetic disk is narrowed. Therefore, the clearance between the magnetic disk and the magnetic head, that is, the flying height of the magnetic head is continuing to be increased. The surface of the magnetic disk is coated with a lubricant to protect magnetically recorded information from damage due to contact with the magnetic head slider.
A magnetic disk device according to a conventional technique, and a lubricant used in the conventional magnetic disk device are described below with reference to FIGS. 17 to 19.
FIG. 17 is a configuration diagram of a general magnetic disk device.
FIG. 18 is a perspective view showing a distal end of a magnetic head 5.
FIG. 19 is a perspective view of the magnetic disk device according to the conventional technique.
As shown in FIG. 17, a plurality of magnetic disks 1 are fixed in stacked form to a magnetic disk rotating shaft 2 connected to a spindle motor (not shown). An arm 4 is actuated about an arm rotating shaft 3. The arm 4 fixed at one end thereof to the arm rotating shaft 3 has a coil (not shown) to actuate the arm 4, and this coil and magnets provided near a housing 10 form a voice coil motor 6 to generate actuating force. The coil, the magnets, and the voice coil motor constitute a rotary actuator. A magnetic head 5 for magnetic disk read/write use is provided at a front end of the arm 4. The magnetic head 5 moves above a magnetic disk 1 to conduct magnetically recorded information read/write operations thereupon. During standby, the magnetic head is stored in a load/unload region 7.
The perspective view showing the distal end of the magnetic head 5 in FIG. 17 represents the distal end existing when viewed from a direction of the magnetic disk 1. A magnetic head slider 8 with a read/write element formed thereon is provided at the distal end of the magnetic head 5. While the magnetic head slider 8 uses an air film lubrication effect to fly along the surface of the magnetic disk 1, the magnetic head conducts magnetically recorded information read/write operations upon the surface of the magnetic disk 1.
FIG. 19 shows the magnetic head slider 8 of FIG. 18 that exists when viewed from a direction of the magnetic disk 1 (i.e. from an upward direction of the slider in FIG. 18). The magnetic head slider 8 has pads 9, through which, an inflow of air from a direction of an arrow in FIG. 19 enters a spatial gap between the magnetic head slider 8 and the magnetic disk 1, proximate to a leading side face 43 of the slider, thus forming an air bearing film effect on an air bearing face 20 of the slider. Therefore, the air flows out from a trailing side face 13 of the slider in FIG. 19. The air bearing film enables the magnetic head slider 8 to fly above the magnetic disk 1.
As described above, the flying height of the magnetic head slider 8 above the magnetic disk 1 has been significantly reduced in recent years. This is causing the event that a part of the lubricant on the magnetic disk is stirred up into the air and sticks to the magnetic head slider. The lubricant sticking thereto poses two serious problems. A first problem is that wetting with the lubricant begins to spread from the surface of the magnetic head slider to an air bearing surface and resultingly changes the flying height. A second problem is that vibration of the magnetic head slider or a flow of surrounding air causes any droplets of the lubricant to fall onto the disk, thus permits the magnetic head slider to get on the disk, and results in a crash.
With respect to the above first problem, JPA-1998-293982 proposes a magnetic disk device that includes magnetic head sliders. According to JP-A-1998-293982, the magnetic disk device described therein is effective for preventing a lubricant from sticking to a trailing edge of a magnetic head slider, since an angle between an air bearing surface and the trailing edge is reduced below 70 degrees to create a smooth airflow near the trailing edge. However, the magnetic disk device disclosed in JP-A-1998-293982 is unable to completely prevent the lubricant from sticking to the magnetic head slider, and has the problem that when the magnetic disk stops rotating, wetting with the lubricant sticking to the trailing edge will spread to the air bearing surface.
In addition, with respect to the above second problem, JP-A-1996-87847 proposes a magnetic head slider constructed so that one face of the slider that connects to a trailing edge thereof above an air bearing surface includes means for retaining a lubricant sticking to the slider. The face of the slider that connects to the trailing edge thereof has a groove or protrusion as the lubricant retaining means. According to JP-A-1996-87847, this suppresses entry of the lubricant sticking to and deposited on the magnetic head, into an interface between the surface of the magnetic disk under a stopped state and the air bearing surface of the magnetic head, thereby enabling stiction to be avoided.
However, even the magnetic head slider described in JP-A-1996-87847 has a problem in that if the groove or protrusion that is the lubricant retaining means has uniform wettability over its entire surface or if the surface in contact with the air bearing surface has high wettability and the lubricant has a nature to spread its wetting, the retained lubricant will spread to the air bearing surface under the stopped state of the disk.
The present invention has been made in order to solve the above problems, and is intended to provide a highly reliable magnetic disk device including a magnetic disk coated with a lubricant, the disk device being adapted to prevent a wetting spread of the lubricant to an air bearing surface and hence, a fall of the lubricant from a magnetic head slider.